Noun
The small space beneath the base line of a subject engraved on a coin or medal. It usually contains the date, place, engraver's name, etc., or other subsidiary matter.
Source: Webster's dictionaryInscription EKTΩP (Hektor) above, IΛIEΩN (Ilion meaning Troy) in exergue. Source: Internet
Many coins do not have an exergue at all, especially those with few or no legends, such as the Victorian bun penny. Source: Internet